Up/Downhill corrections

[goodgrouper]

Yes, I always hunt with the PDA and Exbal and that hunt was dialed in with the computer. I just thought I would mention that hunt because there was one picture I took and posted here of the angle and length of the shot on the mountian and that was only 20 degrees or so. So you would have to shoot up something steeper than that killer mountain to get a shot with more angle and it would be hard to find.

 

[blackco]

THAT'S IT!!! Does anyone know of a good web site for gardening or knitting, or maybe ice carving? /ubbthreads/images/graemlins/smile.gif This long range shooting/hunting just went right over my head. /ubbthreads/images/graemlins/confused.gif Who would ever believe that something as ?"simple?" as sending a piece of lead to a target could get sooo complicated. When I grow up I want to be just like you guys. /ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/smirk.gif /ubbthreads/images/graemlins/grin.gif

 

[Sendero_Man]

www . underwater BB stacking . com

/ubbthreads/images/graemlins/grin.gif

 

[eddybo]

I admit I am way out of my depth of understanding here, but I have a stupid question anyway. What adjustment if any would you have to use if you were using one of those fancy range finders that auto corrects for angle and gives true distance?

 

[Desert Fox]

[ QUOTE ]
I admit I am way out of my depth of understanding here, but I have a stupid question anyway. What adjustment if any would you have to use if you were using one of those fancy range finders that auto corrects for angle and gives true distance?

[/ QUOTE ]

No adjustment needed. Just dial what your rangefinder tells you and shoot.

 

[Desert Fox]

This post made me re-think and analyzed the only extreme angle shot I made on game. The distance is only 618 yards but the angle was at 22 degrees. I was hunting, using my 300 Win Mag Model 70 Laredo LRH. I carried a trajectory table for this rifle shooting the Hornady 180 grain BTSP with a B.C of .452 at 3000 fps, corrected for 3500 ft. elevation - 76 degrees F at 50% humidity. This trajectory table was generated by a ballistic program written by Walter Fenchu, in DOS format. I still have the floppy disc that the program was downloaded to. It's an excellent complete ballistic program. I still used it from time to time. Anyway, it was late in the afternoon at around 7:45PM. the light was fading fast when I spotted the deer; a young 3X2, that just wake-up and was busy playing with two does. I lazered him at 618 yards. At the back of my trajectory table, I have a corresponding angle cosine multiplier, in 5 degree increments, starting from 10,15,20 and so forth up to 45 degree angle. I got my calculator out, yes, I did used a calculator, can you believed that - and punched 618 X .93, the 22 degrees cosine equivalent, which gave me the corrected distance of 574.74 yards. Looking at the trajectory table, the 575 yards, show's 10.2 MOA. The deer was barely visible now from the fast approaching darkness. It probably took me only 2 to 3 minutes, from the time I spotted the deer and did my computation. Anyway the deer gave me all the time in the world. He was busy messing around with the does. I turned the Leupold dial to 10MOA and added one more click, aimed, and then fired. I cycled another round immediately and re-acquired the target just in case but it's not necessary. I could see from looking at the scope, the deer was walking kind of funny and then he just dropped - dead! I have to wait the following day to retrieved the deer since by then it was really dark. Upon inspection-the bullet entered exactly within a few inches of where I aimed. Now I re-inputed all of these data into the Exbal and got .25MOA difference. 10.25 MOA according to my chart against 10.50 MOA from the Exbal. Close enough.

 

[Buffalobob]

Eddybo

[ QUOTE ]
gives true distance?


[/ QUOTE ]

This is where the problem begins in understanding the issue. There are many true distances. The laser measures a "true" straight line distance. It is not the "true" distance the bullet travels. Infact distance is not the chief concern, it is just something you can measure in the field very easily.

The chief concern is the angle of the bullet with respect to gravity and how long gravity has to accelerate the bullet downward. Because the bullet path is not a straight line, but a big looping curve at long range, there is no simple way of accurately calculating the exact effect of gravity on the bullet. Computers can make more complex calculations quicker than one of us out in the field but you must first ascertain whether the guy who wrote the computer program actually KNEW WHAT HE WAS DOING. In the world of computer programming is the saying <font color="red">GARBAGE IN GARBAGE OUT </font> , meaning that a computer is no better than what is put into it. It is not a magic box and there are just as many quack engineers and physicist as there are doctors and lawyers.

I know this does not fully answer your question but I hope it gets you started back to a new basic understanding of the issue.

 

[jwp475]

[ QUOTE ]
I admit I am way out of my depth of understanding here, but I have a stupid question anyway. What adjustment if any would you have to use if you were using one of those fancy range finders that auto corrects for angle and gives true distance?

[/ QUOTE ]

It would give the same answer as useing the cosine for true horrizontal distance and the same aiming error because the bullets time of flight is not calculated as in Shawn's original post..........

 

[eddybo]

Thanks BB and JWP475...that is kind of sorta exactly what I thought, but wanted to be sure. I am not shooting far enough for this factor to be of great conconcern yet, but when I reach those distances I will invest in one of the more advanced ballistics programs.

 

[Shawn Carlock]

Here is the new Nightforce angle indicator. The indicator is produced by Sniper tools and the mount made by Nightforce.

 

[IDAHO PREACHER]

Got a price and availability? IP

 

[Shawn Carlock]

Availability is good I have a couple in the shop and they are 150.00 + shipping. They come only as an indicator and mount only.

 

[Partagas]

Is there a correction factor you could just multiply your cosined adjustment by for bullet time of flight? Or is the bullet time of flight part of it way too complicated w/ too many variables that you need exbal?

I just thought you could make a rough chart for your slope distance to further adjust you cosine adjustment for when the batts go dead on the palm etc.

 

[Shawn Carlock]

I talked with Jeff again today about that and other items. The formula is a complicated mixture of departure angles, trajectory arcs, time of flight and other items. There is also another good point to be made here. While hunting if you want a place to make an error just use some math in the field. I believe the best way to back up the PC is with an Exbal generated angle drop chart printed from the Excell function in the program.